1. Field of the Description
The present invention relates, in general, to methods and systems for sensing the bend of an object such as a human joint (e.g., curling of a person's finger), and, more particularly, to a wireless backscatter bend sensor and systems and methods for processing signals or data from the bend sensor to quantify bend of an object upon which the bend sensor is mounted or attached.
2. Relevant Background
There are numerous settings where it is desirable to sense motion of objects such as whether or not an object is bent and, if so, to what degree is the object bent. For example, it may be desirable to sense the motion of a hand or of fingers of the hand for use in motion capture systems and for use in human computer interaction devices. In other cases, a bend sensor may be used to sense bend in applications requiring monitoring the health or status of a structure.
More specifically, in theme parks and other environments, it would be useful to provide visitors of the park with gloves that can be used to interact with robotic characters, interactive displays, and so on to obtain a user-controlled and immersive entertainment experience. If a bend sensor (or sensors) was imbedded in each finger of the glove, it would be possible to sense when and to what extent the fingers were bent, e.g., wiggle your fingers and a nearby robotic character also wiggles its fingers or otherwise responds to the visitor or glove user's control input. The bend sensing ability would allow the visitors/users to manipulate objects in the nearby environment that may otherwise appear inanimate, thereby creating a unique and exciting experience.
For this exemplary and many other uses, the bend sensor would preferably meet a number of design goals or criteria. First, it may be preferred that the bend sensors be inexpensive so that a park or other facility operator can distribute the sensors without charge or at relatively low fees to the users. The goal of an inexpensive bend sensor may also be furthered by eliminating or limiting the amount of conventional electronics typically provided with sensors such as analog-to-digital converters, amplifiers, and the like. Second, the bend sensor may be designed to have low power consumption and even be passive in some cases (e.g., not require a battery or other bulky and costly power source). Third, the use of the bend sensor may be adapted or configured such that the resolution and/or the degrees of freedom may be relatively low, which will also further the first and/or second goals of lower costs and low power consumption by simplifying the sensor design. Fourth, it typically is preferable that communications between the sensor and processor/controller be wireless such that the user is free to move about their environment.
Previous bend sensors have typically not met one or more of these goals with many bend sensors being costly, requiring significant amounts of power (e.g., an onboard battery), providing high resolution and degrees of freedom (adding to complexity of the design and output signal processing), and using a wired or direct communication link between the sensors and the processor/controller. With regard to hand joints, gloves have been designed and produced to sense the angle of hand joints or bend of fingers. These gloves are often referred to as data gloves and may utilize fiber optics linked to a processor or sensors relying on piezoresistive materials, such as conductive elastomers, conductive ink, sliding resistors, and conductive fluid. In other cases, such as for use with robotic devices, numerous strain gauges may be provided on or near joints. Each of these solutions to monitoring or sensing bend or motion may be expensive to design and manufacture, thereby limiting their use in many situations where cost is a significant parameter.
Hence, there remains a need for a bend sensor that meets the demand for a wireless sensor that can be implemented at low cost. Preferably, such a sensor would be passive or semi-passive and not require an onboard power source or a charge pump. The sensor, in some cases, may also be relatively low resolution with its output or sensing signals leading to less complex processing to determine sensed bending or movement of a monitored joint or other object.